1. Field of the Invention
The invention relates generally to methods, devices and materials for use in treating pleural effusion.
2. Description of the Related Art
In the thoracic cavity, a layer of visceral pleura covers the surface of the lung, and a layer of parietal pleura lines the inner surface of the thoracic cavity, including the inside of the ribs and diaphragm. These smooth membranes normally contain a small amount of clear, plasma-like pleural fluid that helps reduce the friction between the lung surface and its surroundings as the lung expands and contracts with respiration. The accumulation of an abnormal amount of fluid between the visceral and parietal pleuras is called pleural effusion. For example, a patient with lung cancer can have a plurality of parietal or visceral lesions that produce clear fluid that gets into the pleural space.
The etiology of pleural effusions is varied and includes congestive heart failure, pneumonia, and pulmonary malignancies among others. Patients with pleural effusion often present with dyspnea, minimal to moderate chest pain, dullness on percussion and possible pleural friction rub and/or mediastinal shift. The existence of an effusion can generally be confirmed with chest radiography or CT. There is significant potential for morbidity and mortality due to the tendency for the volume of the pleural effusion fluid to compress the lungs, thereby restricting their expansion.
If the pleural effusion is recurring or is caused by a progressive pulmonary malignancy, pleurodesis is generally indicated. Pleurodesis is a therapeutic procedure involving drainage of the pleural fluid and introduction of a sclerosing agent between the two pleural membranes to cause a scarring reaction, which effectively fuses the two layers to one another. The goal is to close the pleural space and preclude fluid from entering it again. See, e.g., U.S. Pat. No. 5,484,401, which describes some prior treatments for pleural effusion. Current treatments include, for example, surgical intervention to drain the fluid, distribute talc into the pleural space, draw a vacuum, and then monitor the patient in the hospital.
A variety of agents are currently used to perform chemical pleurodesis, including radioactive isotopes, tetracycline, chemotherapeutic agents and talc. Two things are necessary for a successful pleurodesis: (1) The sclerosing agent must be evenly distributed across the pleural surfaces; and (2) the lung must still be able to expand effectively after the procedure.
Treatment for pleural effusion currently involves introduction of a chest tube through the chest wall into the pleural space, followed by drainage of the fluid. The chest tube is then clamped, allowing the lung to partially collapse. A syringe containing a sclerosing agent is attached to the chest tube, and the agent is insufflated into the pleural space. The chest tube is unclamped, allowing the lung to inflate fully and to pull the agent further into the pleural space. The patient is rotated in bed over the following few hours to assist in the equal distribution of the agent. The chest tube is removed when there is less than 100 cm3 of fluid per day removed from the pleural space. This pleurodesis procedure may be done at the bedside.
The sclerosing agents irritate the pleural membranes, eventually causing them to become inflamed and scarred, which fuses the layers together. Talc is the most commonly used sclerosing agent and has a reported 90% success rate. Although talc has demonstrated a high rate of success, there are complications associated with the procedure, most of which are caused by the sclerosing agent and the nature of its action. Patients commonly experience pain during the installation of the agent, which is very irritating and inflammatory, and a narcotic is therefore usually administered prior to the procedure. Also, fever is common in more than 30% of patients undergoing talc pleurodesis, possibly due to the pleuritis it causes. The fever generally lasts for approximately 48 hours.
It is difficult to evenly distribute most sclerosing agents, especially talc, because they do not flow. Talc does not mix well with saline and has a tendency to clump. Incomplete lung expansion due to a partially trapped lung can occur when pleurodesis is only partially successful.
Additionally, pleurodesis is performed over several days. While waiting for the full effects of the scarring action to take place, the patient is in danger of partial or full respiratory failure. Thus, hospitalization and close monitoring is required during this period.
What is needed, therefore, is a device for distributing sclerosing agents which reduces the risk of partial or full respiratory failure.